Refrigerant throttling device

ABSTRACT

A refrigerant restriction device for use in a refrigeration system, the restriction device comprising a member having a bore of predetermined length and diameter therein with a conical inlet and a conical outlet to effect the desired pressure drop between the high and low pressure sides of the system.

United States Patent Amick 1 Feb. I5, 1972 [54] REFRIGERANT THROTTLING DEVICE [72] Inventor: Larry D. Amick, Brownsburg, Ind.

[73] Assignee: Carrier Corporation, Syracuse, NY.

[22] Filed: Apr. 15, 1970 [21] Appl. No.: 28,898

52] us. c1 ..l38/45, 2/511 Field of Search ..l38/45, 44; 62/511 [56] References Cited UNITED STATES PATENTS 2,796,463 4/1957 Delzno ..l38/44 1,971,159 8/1934 Laurent ..l38/44 2,781,058 2/1957 Warhus ..62/511 3,444,897 5/1969 Erickson 138/45 Primary Examiner-Meyer Perlin Attorney-Harry 6. Martin, Jr. and .1. Raymond Cu 'n [57] ABSTRACT A refrigerant restriction device for use in a refrigeration system, the restriction device comprising a member having a bore of predetennined length and diameter therein with a conical inlet and a conical outlet to effect the desired pressure drop between the high and low pressure sides of the system.

6 Claims, 6Drawingliglu'es REFRIGERANT THROT'ILING DEVICE BACKGROUND OF THE INVENTION A variety of restriction or refrigerant flow control devices are utilized in small refrigeration systems, the most popular being thermoexpansion valves and capillary tubes. Thermoexpansion valves respond to the temperature of the refrigerant gas leaving the evaporator and the pressure in the evaporator to control refrigerant flow to the evaporator. The thermoexpansion valve therefore includes pressure sensing and temperature sensing means which result in a fairly complex and expensive valve.

Capillary tubes may be utilized to provide an inexpensive restriction device in suitable refrigeration systems. However, capillaries are most effective over a very narrow temperature range and require a precise quantity of refrigerant in the refrigeration system for proper refrigerant control. For this reason, capillaries are most often used in window-type room air conditioners, refrigerators and packaged refrigeration systems which are completely assembled at the factory where cleanliness can be assured and systems can be precisely charged with refrigerant. Even under optimum conditions, the small bores in the capillaries may be easily damaged or may be obstructed by particulate matter that may be present in the system.

The use of capillary control in refrigeration systems has in recent years been increasing in the split" type system wherein a condensing unit is located remote from the evaporator coil and suitable refrigerant lines interconnect the condensing unit with the evaporator coil. By utilizing precharged refrigerant system components and mechanical connectors on the refrigerant lines to minimize or prevent loss of refrigerant therefrom or entrance of contaminants therein, capillary control of the system may be advantageously and economically employed. However, since the capillary provides optimum refrigerant flow over a very narrow range, a large inventory of packaged evaporator coils having capillary tubes associated therewith must be maintained for accurately matching the evaporator coil with the refrigeration load to be satisfied.

SUMMARY OF THE INVENTION This invention relates to a refrigerant restriction device to control refrigerant flow between the highand low-pressure sides of a refrigeration system. The restriction device includes a body adapted to receive an insert member therein. The insert member is provided with a bore of predetermined length and diameter having a conical inlet and'a conical outlet com municating therewith. The length of the bore is between five and 30 times the inside diameter of the bore.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of a refrigeration system employing the refrigerant restriction device of the present invention to provide the requisite pressure drop across the system;

FIG. 2 is a sectional view of the body of the refrigerant expansion device illustrated in FIG. 1;

FIG. 3 is a sectional view of the restriction insert member adapted for placement within the body of FIG. 2;

FIG. 4 is a schematic of a refrigeration system having a capillary controlled evaporator utilizing the refrigerant restriction device of the present invention to reduce the capacity of the evaporator coil;

FIG. 5 is a sectional view of the body of the refrigerant restriction device illustrated in FIG. 4; and

FIG. 6 is a sectional view of the insert member adapted for insertion in the body of FIG. 5.

-of my invention, disclose a refrigerant compressor 2, a condenser coil 4, and an evaporator coil 6, connected to provide refrigeration. A refrigerant restriction device 8 is disposed between condenser coil 4 and evaporator coil 6 to provide the requisite pressure drop therebetween. The refrigerant restriction device 8, which is more clearly illustrated in FIGS. 2 and 3, is comprised of a body 10 having external threads 12 on each end thereof for mating engagement with flare fittings 14 provided in the refrigerant lines interconnecting condenser coil 4 with evaporator coil 6. An insert member 16, illustrated in FIG. 3, is adapted to be suitably secured within bore 11 of body 10 by suitable means such as an interference fit or by brazing. The insert member 16 is provided with a bore 18 of predetermined length and diameter having a conical inlet 20 and a conical outlet 22. The conical inlet 20 and the conical outlet 22 have an included angle or within the range of 45 to 75.

The insert member, having a bore of predetermined length and diameter and a conical inlet and outlet, provides an expansion device with a very predictable flow rate in a refrigeration system. The flow rate therethrough responds to changes in refrigerant subcooling and system high side pressure to maintain equilibrium in the refrigeration system. The bore in the insert member is sized so that the liquid refrigerant flowing therethrough reaches critical velocity to prevent downstream pressure conditionsfrom effecting the flow rate through the device. The conical inlet and outlet are very important to the predictability and repeatability of the device. The conical inlet accelerates the refrigerant gradually to reduce the effects of sharp edges and roughness encountered on square edge inlet expansion devices. The conical outlet provides for a smooth, rapid deceleration of the refrigerant flow through the insert to prevent refrigerant discharge from the insert from adversely affecting refrigerant flow through the bore section thereof. Further, the rapid deceleration of the refrigerant results in a refrigerant phase change fairly close to the discharge of the insert member so that a refrigerant vapor distributor may be located directly downstream from the insert, if desired.

For optimum system performance, the maximum inlet diameter of the conical inlet and the maximum outlet diameter of the conical outlet should be maintained within the range of two to three times the inside diameter of the bore. The length of the bore should be maintained within a range of five to 30 times the diameter of the bore. The inside diameter and the length of the bore are selected for the refrigerant flow rates required in the system in which the restriction device is employed. As an example, an insert member having a bore diameter of 0.076 inches, a length of 1.625 inches, a conical inlet having an included angle of 60 and a maximum diameter of 0.l90, and aconical outlet having an included angle of 60 and a maximum diameter of 0.l90, will provide the requisite pressure drop for a 4 ton refrigeration system utilizing refrigerant 22 (Monochlorodifluoromethane).

The restriction device is similar to a capillary tube, but differs in that the pressure differential across the restriction device is caused primarily by the inlet restriction cone and the outlet expansion cone, and secondarily by the friction through the bore. The restriction provided by a capillary tube results almost exclusively due to the friction through the bore, while a very small percentage of the restriction is caused by the unavoidable imperfections in the capillary inlet and outlet. In a capillary, the refrigerant ordinarily changes phase within the tube so that refrigerant discharged therefrom is in vapor form. Refrigerant distribution to the evaporator coil is therefore easily accomplished.

In a sharp-edged orifice restriction device, the pressure drop thereacross is almost exclusively caused by the inlet and discharge edges of the orifice. With a sharp-edged orifice, refrigerant phase change occurs a considerable distance downstream from the orifice. This requires a fairly large distance between the orifice and the distributor to assure proper distribution of refrigerant vapor to the various circuits of the evaporator coil. A further problem in utilizing a sharpedged orifice in a refrigeration system is the tolerance and accuracy of the orifice edges necessary to produce a predictable and accurate flow restriction device for refrigerant.

The disclosed flow restriction device overcomes or obviates the refrigerant flow control problems inherent in both capillary tubes and sharp-edged orifices, while providing an accurate and inexpensive means for regulating refrigerant flow in a refrigeration system.

The restriction device described heretofore may also be utilized in conjunction with a capillary controlled evaporator coil package to reduce the capacity of the evaporator coil when a coil of the required capacity is not available and a larger coil must be substituted but the capacity thereof reduced for proper system operation.

Referring to FIGS. 4, 5 and 6, there is illustrated a refrigerant compressor 42, a condenser coil 44, and an evaporator coil 46, connected to provide refrigeration. The evaporator coil 46 is provided with a refrigerant distributor 48 and capillary tubes 50 for distributing and controlling the flow of refrigerant to the evaporator coil 46. A refrigerant restriction device 52 is disposed between condenser coil 44 and refrigerant distributor 48 to reduce the capacity of evaporator coil 46. The refrigerant restriction device 52, which is more clearly illustrated in FIGS. 5 and 6, is comprised of a body 54 having internal threads 56 on one end thereof for mating engagement with external threads on refrigerant distributor 48 and external threads 58 for mating engagement with a flare fitting 60 provided on the liquid refrigerant line from con denser coil 44. An insert member 62, illustrated in FIG. 6, is adapted to be suitably secured within bore 64 of body 54 by suitable means, such as an interference fit or by brazing. The insert 62 is provided with a bore 66 of predetermined length and diameter having a conical inlet 68 and a conical outlet 70. The conical inlet 68 and the conical outlet 70 have an included angle (1 within the range of 45 to 75.

It can be seen from the foregoing that the refrigerant restriction device 52 illustrated in FIG. 4 is basically identical to the refrigerant restriction device 8 illustrated in FIG. 1.

I claim:

1. A refrigerant restriction means to control refrigerant flow between highand low-pressure sides of a refrigeration system comprising a member having a bore of predetermined length and diameter therethrough, said member having a conical inlet and a conical outlet formed therein, the length of the bore being between five and thirty times the inside diameter of the bore.

2. A refrigerant restriction means according to claim I wherein the maximum diameter of the conical outlet is within a range of two to three times the diameter of the bore.

3. A refrigerant restriction means according to claim 2 wherein the maximum diameter of the conical inlet is within a range of two to three times the diameter of the bore.

4. A refrigerant restriction means according to claim 3 wherein the conical inlet has an included angle within the range of 45 to 75.

5. A refrigerant restriction means according to claim 2 wherein the conical outlet has an included angle within the range of 45 to 75.

6. A refrigerant restriction means according to claim 5 wherein the conical outlet has an included angle within the range of 45 to 75, said restriction device further including a body having a bore therein for receiving said-member, said body having threads formed on both ends thereof for connection to threaded flare fittings for installing the restriction device in a refrigeration system. 

1. A refrigerant restriction means to control refrigerant flow between high- and low-pressure sides of a refrigeration system comprising a member having a bore of predetermined length and diameter therethrough, said member having a conical inlet and a conical outlet formed therein, the length of the bore being between five and thirty times the inside diameter of the bore.
 2. A refrigerant restriction means according to claim 1 wherein the maximum diameter of the conical outlet is within a range of two to three times the diameter of the bore.
 3. A refrigerant restriction means according to claim 2 wherein the maximum diameter of the conical inlet is within a range of two to three times the diameter of the bore.
 4. A refrigerant restriction means according to claim 3 wherein the conical inlet has an included angle within the range of 45* to 75*.
 5. A refrigerant restriction means according to claim 2 wherein the conical outlet has an included angle within the range of 45* to 75*.
 6. A refrigerant restriction means according to claim 5 wherein the conical outlet has an included angle within the range of 45* to 75*, said restriction device further including a body having a bore therein for receiving said member, said body having threads formed on both ends thereof for connection to threaded flare fittings for installing the restriction device in a refrigeration system. 